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Ton-miles while making short trip

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The ton-miles of work performed in short trip operation is also in term of round trips.

The ton-miles of work done in making a short trip is equal to the difference between round ton-miles of end depth and starting depth. The formula for short trip ton-miles is listed below;

Tst = T6 – T5

Where; Tst = ton-miles for short trip
T6 = ton-miles for one round trip at the deeper depth
T5 = ton-miles for one round trip at the shallower depth

Example;

Please determine short trip ton-miles from 8000 ft to 8050 ft
Ton-miles @ 8050 ft = 200
Ton-miles @ 8000 ft = 190
Tst = (200 – 190)
Tst = 10 ton-miles
Ref book: Drilling Formula Book Formulas and Calculations for Drilling, Production and Workover, Second Edition

Ton-Miles for Setting Casing

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For the setting casing operation, the ton-miles calculation of this operation is similar to round trip ton-miles calculation. Nevertheless, buoyed weight of the casing will be used into calculation instead of buoyed weight of drill pipe and with the result will be multiplied by 0.5, because setting casing is just only one-way operation (1/2 round trip).

Ton-miles for setting casing can be determined from the following formula:

Tc = {Wp x D x (Lcs + D) + D x Wb} x 0.5 ÷ (5280 x 2000)

Where; Tc = ton-miles setting casing
Wp = buoyed weight of casing in lb/ft
Lcs = length of one joint of casing in ft
Wb = weight of travelling block assembly in lb
D = depth of casing in ft
2000 = number of pounds in one ton
5280 = number of feet in one mile

Example: Ton-Miles for Setting Casing

Mud weight = 10.0 ppg
Casing weight = 25.0 lb/ft
Depth of casing = 5200 ft
Travelling block assembly = 95,000 lb
Length of one joint of casing = 42 ft

Solution:

a) Buoyancy factor:
BF = (65.5 – 10.0) ÷ 65.5
BF = 0.8473

b) Buoyed weight of casing in mud, lb/ft (Wp):
Wp = 25.0 lb/ft x 0.8473
Wp = 21.18 lb/ft

c) Casing ton-miles
Tc = {21.18 x 5,200 x (42 + 5,200) + 5,200 x 95,000} x 0.5 ÷ (5280 x 2000)
Tc = 50.73 tone-miles

Ton-Mile (TM) for Setting Casing Calculation Sheet

Ref book: Drilling Formula Book Formulas and Calculations for Drilling, Production and Workover, Second Edition